RESUMO
Metastable noble metal nanocrystals may exhibit distinctive catalytic properties to address the sluggish kinetics of many important processes, including the hydrogen evolution reaction under alkaline conditions for water-electrolysis hydrogen production. However, the exploration of metastable noble metal nanocrystals is still in its infancy and suffers from a lack of sufficient synthesis and electronic engineering strategies to fully stimulate their potential in catalysis. In this paper, we report a synthesis of metastable hexagonal Pt nanostructures by coherent growth on 3d transition metal nanocrystals such as Ni without involving galvanic replacement reaction, which expands the frontier of the phase-replication synthesis. Unlike noble metal substrates, the 3d transition metal substrate owns more crystal phases and lower cost and endows the hexagonal Pt skin with substantial compressive strains and programmable charge density, making the electronic properties particularly preferred for the alkaline hydrogen evolution reaction. The energy barriers are greatly reduced, pushing the activity to 133 mA cmgeo-2 and 17.4 mA µgPt-1 at -70 mV with 1.5 µg of Pt in 1 M KOH. Our strategy paves the way for metastable noble metal catalysts with tailored electronic properties for highly efficient and cost-effective energy conversion.
RESUMO
Promoting the formation of high-oxidation-state transition metal species in a hydroxide catalyst may improve its catalytic activity in the oxygen evolution reaction, which remains difficult to achieve with current synthetic strategies. Herein, we present a synthesis of single-layer NiFeB hydroxide nanosheets and demonstrate the efficacy of electron-deficient boron in promoting the formation of high-oxidation-state Ni for improved oxygen evolution activity. Raman spectroscopy, X-ray absorption spectroscopy, and electrochemical analyses show that incorporation of B into a NiFe hydroxide causes a cathodic shift of the Ni2+(OH)2 â Ni3+δOOH transition potential. Density functional theory calculations suggest an elevated oxidation state for Ni and decreased energy barriers for the reaction with the NiFeB hydroxide catalyst. Consequently, a current density of 100 mA cm-2 was achieved in 1 M KOH at an overpotential of 252 mV, placing it among the best Ni-based catalysts for this reaction. This work opens new opportunities in electronic engineering of metal hydroxides (or oxides) for efficient oxygen evolution in water-splitting applications.
RESUMO
Osteosarcoma (OS) is the predominant form of primary bone malignancy in children and adolescents. Although the combination of chemotherapy and modified surgical therapy leads to marked improvements in the survival rate, the therapeutic outcomes remain unsatisfactory. Therefore, the identification of novel drugs with higher efficacy and fewer sideeffects is urgently required. Proteasome inhibitors have been approved by the Food and Drug Administration (FDA) for the treatment of certain cancers, although none of them are directed against OS. Noncovalent proteasome inhibitors, such as PI1840, are superior to covalent ones in numerous respects in view of their chemical structure; however, to date, no studies have been published on the effects of noncovalent proteasome inhibitors on OS cells. In the present study, the antineoplastic effects of PI1840 were systematically evaluated in the OS cell lines, MG63 and U2OS. Cell viability and morphological changes were assessed by Cell Counting Kit8 (CCK8) and live/dead assays. The cell cycle was analyzed using flow cytometry (FCM) and western blot analysis (assessing the levels of the proteins p21, p27, and the tyrosine kinase, WEE1). The extent of cell apoptosis and autophagy were assessed by FCM, western blot analysis [of the apoptosisassociated proteins, microtubuleassociated protein 1 light chain 3 α (LC3) and Beclin1], and mRFPGFPLC3 adenovirus transfection assay. Transwell and wound healing assays, and western blot analysis of the matrix metalloproteinases (MMPs)2 and 9 were performed to preliminarily evaluate the migration and invasion capability of the cells. In the present study, our results revealed that PI1840 inhibited the proliferation of OS cells and induced apoptosis, partly due to attenuation of the nuclear factorκB (NFκB) pathway. In addition, PI1840induced autophagy was detected, and inhibiting the autophagy of the OS cells led to an increase in the survival rate of the U2OS cells rather than of the MG63 cells. Furthermore, PI1840 attenuated the migration and invasion capabilities of the OS cells. In conclusion, the present study revealed PI1840 to be a promising drug for the treatment of OS.
Assuntos
Acetamidas/farmacologia , Antineoplásicos/farmacologia , Neoplasias Ósseas/tratamento farmacológico , Osteossarcoma/tratamento farmacológico , Oxidiazóis/farmacologia , Inibidores de Proteassoma/farmacologia , Acetamidas/uso terapêutico , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Neoplasias Ósseas/patologia , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Osteossarcoma/patologia , Oxidiazóis/uso terapêutico , Inibidores de Proteassoma/uso terapêuticoRESUMO
Ultra-small platinum nanoparticles loaded over titania is a promising catalyst for the low-temperature water-gas shift (WGS) reaction and shows the potential to work in a mobile hydrogen fuel cell system. Their precise size engineering (<3 nm) and reliable stabilization remain challenging. To address these issues, we report a reverse-micelle synthesis approach, which affords uniform ultra-small platinum nanoparticles (tunable in â¼1.0-2.6 nm) encapsulated in hollow titania nanospheres with a shell thickness of only â¼3-5 nm and an overall diameter of only â¼32 nm. The Pt@TiO2 yolk/shell nanostructured catalysts display extraordinary stability and monotonically increasing activity with the decreasing size of the Pt nanoparticles in the WGS. The size-dependent variation in the electronic property of the Pt nanoparticles and the reducible oxide encapsulation that prevents the Pt nanoparticles from sintering are ascribed as the main reasons for the excellent catalytic performance.
RESUMO
We have developed a robust method for the synthesis of silica nanotubes with controlled aspect ratios on a large scale by templating against rod-like nanocrystals. Crystalline nanorods of a nickel-hydrazine complex are first formed in reverse micelles by surfactant capping on side facets, and subsequent silica coating and selective etching give rise to silica nanotubes of high uniformity and yield. The length of the silica nanotubes is tunable in the range 37-340 nm and can reach as long as micrometers. Control of the length is conveniently achieved by tuning the hydrazine/nickel ratio, which affects the growth kinetics of the nanocrystal templates. The inner diameter of the silica nanotubes can be adjusted in the range 10-20 nm by choosing different surfactants. This method is unique in utilizing reverse micelles as discrete nanoscale reactors for the growth of nanocrystals, allowing for precise control of the features of the nanotubes and opening up new opportunities in the synthesis of novel anisotropic nanomaterials, construction of nanodevices, and potential drug delivery applications.